Induction of Bim and Bid gene expression during accelerated apoptosis in severe sepsis

High-dose Vitamin C injection ameliorates against sepsis-induced myocardial injury by anti-apoptosis, anti-inflammatory and pro-autophagy through regulating MAPK, NF-κB and PI3K/AKT/mTOR signaling pathways in rats

AIMS

This study aimed to evaluate the effects of VC on SIMI in rats.

METHODS

In this study, the survival rate of high dose VC for SIMI was evaluated within 7 days. Rats were randomly assigned to three groups: Sham group, CLP group, and high dose VC (500 mg/kg i.v.) group. The animals in each group were treated with drugs for 1 day, 3 days or 5 days, respectively. Echocardiography, myocardial enzymes and HE were used to detect cardiac function. IL-1β, IL-6, IL-10 and TNF-α) in serum were measured using ELISA kits. Western blot was used to detect proteins related to apoptosis, inflammation, autophagy, MAPK, NF-κB and PI3K/Akt/mTOR signaling pathways.

RESULTS

High dose VC improved the survival rate of SIMI within 7 days. Echocardiography, HE staining and myocardial enzymes showed that high-dose VC relieved SIMI in rats in a time-dependent manner. And compared with CLP group, high-dose VC decreased the expressions of pro-apoptotic proteins, while increased the expression of anti-apoptotic protein. And compared with CLP group, high dose VC decreased phosphorylation levels of Erk1/2, P38, JNK, NF-κB and IKK α/β in SIMI rats. High dose VC increased the expression of the protein Beclin-1 and LC3-II/LC3-I ratio, whereas decreased the expression of P62 in SIMI rats. Finally, high dose VC attenuated phosphorylation of PI3K, AKT and mTOR compared with the CLP group.

SIGNIFICANCE

Our results showed that high dose VC has a good protective effect on SIMI after continuous treatment, which may be mediated by inhibiting apoptosis and inflammatory, and promoting autophagy through regulating MAPK, NF-κB and PI3K/AKT/mTOR pathway.

Xuebijing injection protects against sepsis induced myocardial injury by regulating apoptosis and autophagy via mediation of PI3K/AKT/mTOR signaling pathway in rats

OBJECTIVE

Apoptosis and autophagy are significant factors of sepsis induced myocardial injury (SIMI). XBJ improves SIMI by PI3K/AKT/mTOR pathway. Present study is devised to explore the protective mechanism of XBJ in continuous treatment of SIMI caused by CLP.

METHODS

Rat survival was first recorded within 7 days. Rats were randomly assigned to three groups: Sham group, CLP group, and XBJ group. The animals in each group were divided into 12 h group, 1 d, 2 d, 3 d and 5 d according to the administration time of 12 hours, 1 day, 2 days, 3 days or 5 days, respectively. Echocardiography, myocardial injury markers and H&E staining were used to detect cardiac function and injury. IL-1β, IL-6 and TNF-α in serum were measured using ELISA kits. Cardiomyocyte apoptosis was assayed by TUNEL staining. Apoptosis and autophagy related proteins regulated by the PI3K/AKT/mTOR signaling pathway were tested using western blot.

RESULTS

XBJ increased the survival rate in CLP-induced septic Rat. First of all, the results of echocardiography, H&E staining and myocardial injury markers (cTnI, CK, and LDH levels) showed that XBJ could effectively improve the myocardial injury caused by CLP with the increase of treatment time. Moreover, XBJ significantly decreased the levels of serum inflammatory cytokines IL-1β, IL-6 and TNF-α in SIMI rats. Meanwhile, XBJ downregulated the expression of apoptosis-related proteins Bax, Cleaved-Caspase 3, Cleaved-Caspase 9, Cytochrome C and Cleaved-PARP, while upregulated the protein levels of Bcl-2 in SIMI rats. And, XBJ upregulated the expression of autophagy related protein Beclin-1 and LC3-II/LC3-I ratio in SIMI rats, whereas downregulated the expression of P62. Finally, XBJ administration downregulated the phosphorylation levels of proteins PI3K, AKT and mTOR in SIMI rats.

CONCLUSIONS

Our results showed that XBJ has a good protective effect on SIMI after continuous treatment, and it was speculated that it might be through inhibiting apoptosis and promoting autophagy via, at least partially, activating PI3K/AKT/mTOR pathway in the early stage of sepsis, as well as promoting apoptosis and inhibiting autophagy via suppressing PI3K/AKT/mTOR pathway in the late stage of sepsis.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

Functional proteomic profiling links deficient DNA clearance with increased mortality in individuals with severe COVID-19 pneumonia

The factors that influence survival during severe infection are unclear. Extracellular chromatin drives pathology, but the mechanisms enabling its accumulation remain elusive. Here, we show that in murine sepsis models, splenocyte death interferes with chromatin clearance through the release of the DNase I inhibitor actin. Actin-mediated inhibition was compensated by upregulation of DNase I or the actin scavenger gelsolin. Splenocyte death and neutrophil extracellular trap (NET) clearance deficiencies were prevalent in individuals with severe COVID-19 pneumonia or microbial sepsis. Activity tracing by plasma proteomic profiling uncovered an association between low NET clearance and increased COVID-19 pathology and mortality. Low NET clearance activity with comparable proteome associations was prevalent in healthy donors with low-grade inflammation, implicating defective chromatin clearance in the development of cardiovascular disease and linking COVID-19 susceptibility to pre-existing conditions. Hence, the combination of aberrant chromatin release with defects in protective clearance mechanisms lead to poor survival outcomes.

Identifying Potential Effective Diagnostic and Prognostic Biomarkers in Sepsis by Bioinformatics Analysis and Validation

Purpose

Sepsis is a serious life-threatening condition characterised by multi-organ failure due to a disturbed immune response caused by severe infection. The pathogenesis of sepsis is unclear. The aim of this article is to identify potential diagnostic and prognostic biomarkers of sepsis to improve the survival of patients with sepsis.

Methods

We downloaded 7 datasets from Gene Expression Omnibus database and screened the immune-related differential genes (IRDEGs). The related functions of IRDEGs were analyzed through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). CIBERSORT was used to evaluate the infiltration of the immune cells, and Pearson algorithm of R software was used to calculate the correlation between the immune cell content and gene expression to screen the genes most related to immune cells in sepsis group, which were intersected with IRDEGs to obtain common genes. Key genes were identified from common genes based on the area under the receiver operating characteristic curve (AUC) greater than 0.8 in the 6 datasets. We then analyzed the predictive value of key genes in sepsis survival. Finally, we verified the expression of key genes in patients with sepsis by PCR analysis.

Results

A total of 164 IRDEGs were obtained, which were associated mainly with inflammatory and immunometabolic responses. Ten key genes (IL1R2, LTB4R, S100A11, S100A12, SORT1, RASGRP1, CD3G, CD40LG, CD8A and PPP3CC) were identified with high diagnostic efficacy. Logistic regression analysis revealed that six of the key genes (LTB4R, S100A11, SORT1, RASGRP1, CD3G and CD8A) may affect the survival prognosis of sepsis. PCR analysis confirmed that the expression of seven key genes (IL1R2, S100A12, RASGRP1, CD3G, CD40LG, CD8A and PPP3CC) was consistent with microarray outcome.

Conclusion

This study explored the immune and metabolic response mechanisms associated with sepsis, and identified ten potential diagnostic and six prognostic genes.

Blood Bcl-2 levels to predict the mortality of septic patients

Aim: To determine whether blood concentrations of Bcl-2 during the 1st week of sepsis could help predict mortality. Methods: Serum Bcl-2 concentrations were determined at the 1st, 4th and 8th days of sepsis diagnosis. Results: Thirty-day surviving patients (n = 168) showed higher serum Bcl-2 levels at the 1st (p = 0.002), 4th (p < 0.001) and 8th days (p < 0.001) of sepsis diagnosis than non-surviving patients (n = 91). An association between serum Bcl-2 concentrations at the 1st (p = 0.003), 4th (p < 0.001) and 8th days (p = 0.01) and 30-day mortality after controlling for diabetes mellitus, Sepsis-related Organ Failure Assessment, lactic acid and age was found in the multiple logistic regression analysis. Conclusions: The novel finding is that blood Bcl-2 concentrations at any time in the 1st week of sepsis are associated with mortality.

Changes of CD3+CD56+ γδ T cell number and apoptosis during hospital admission are related to mortality in septic patients

Immunoparalysis and apoptosis of T cells are serious problems for the evolution of septic patients. We aimed to relate changes in the number of αβ and γδ T cells during hospital stay to the poor evolution of sepsis. In this prospective study, we recruited a total of 92 septic patients from the Emergency and Intensive Care Departments of two Hospitals, according to the latest criteria for the definition and management of sepsis. According to the severity of the septic process, there was a progressive decrease in T cells, being much more intense in γδ T cells. This decrease recovered in surviving patients, but CD3+CD56+ γδ T cells continued to decreased during hospital stay in non-surviving patients. Apoptosis increased in sepsis. Cell death of CD3+CD56+ γδ T cells progressively increased according to the severity of sepsis, especially in non-surviving patients.

Circulating Bcl-2 concentrations and septic patient mortality

INTRODUCTION

There are not data on blood B-cell lymphoma 2 (Bcl-2) concentrations (one of the antiapoptotic molecules of the Bcl-2 family in the intrinsic apoptosis pathway) in septic patients. Therefore, this study was carried with the aims to explore whether blood Bcl-2 concentrations at diagnosis of sepsis are different in survivor and non-survivor septic patients, are associated with mortality, and are useful for the mortality prediction.

METHODS

Intensive Care Units from 3 Spanish hospitals participated in this observational and prospective study with septic patients and serum Bcl-2 concentrations at diagnosis of sepsis were determined. Mortality at 30 days was as outcome variable.

RESULTS

We found that 30-day non-surviving patients (n=81) showed lower serum Bcl-2 levels (p=0.003) than surviving patients (n=140). We found that serum concentrations of Bcl-2<4.4ng/mL were associated with mortality (OR=3.228; 95% CI=1.406-7.415; p=0.006) in the multiple logistic regression analysis, and that showed an area under the curve for mortality prediction of 62% (95% CI=55-68%; p=0.003).

CONCLUSIONS

In our study appears novel findings such as higher blood Bcl-2 concentrations in survivor than in non-survivor septic patients, the association between low blood Bcl-2 concentrations and mortality of septic patients, and the ability of blood Bcl-2 concentrations for the prediction of septic patient mortality.

Immune Intervention in Sepsis

Sepsis is a host immune disorder induced by infection. It can lead to multiple organ dysfunction syndrome (MODS), which has high morbidity and mortality. There has been great progress in the clinical diagnosis and treatment of sepsis, such as improvements in pathogen detection technology, innovations regarding anti-infection drugs, and the development of organ function support. Abnormal immune responses triggered by pathogens, ranging from excessive inflammation to immunosuppression, are recognized to be an important cause of the high mortality rate. However, no drugs have been approved specifically for treating sepsis. Here, we review the recent research progress on immune responses in sepsis to provide a theoretical basis for the treatment of sepsis. Constructing and optimizing a dynamic immune system treatment regimen based on anti-infection treatment, fluid replacement, organ function support, and timely use of immunomodulatory interventions may improve the prognosis of sepsis patients.

Immune Cell Number, Phenotype, and Function in the Elderly with Sepsis

Sepsis is a form of life-threatening organ dysfunction caused by dysregulated host responses to an infection that can be partly attributed to immune dysfunction. Although sepsis affects patients of all ages, elderly individuals display increased susceptibility and mortality. This is partly due to immunosenescence, a decline in normal immune system function associated with physiological aging that affects almost all cell types in the innate and adaptive immune systems. In elderly patients with sepsis, these alterations in immune cells such as endothelial cells, neutrophils, monocytes, macrophages, natural killer cells, dendritic cells, T lymphocytes, and B lymphocytes, are largely responsible for their poor prognosis and increased mortality. Here, we review recent studies investigating the events affecting both innate and adaptive immune cells in elderly mice and patients with sepsis, including alterations in their number, phenotype, and function, to shed light on possible new therapeutic strategies.

Is lymphopenia different between SARS and COVID-19 patients?

Lymphopenia is commonly observed in SARS and COVID‐19 patients although the lymphocyte count is not always below 0.8 × 10⁹/L in all the patients. It is suggested that lymphopenia serves as a useful predictor for prognosis in the patients. It is also hypothesized that lymphopenia is related to glucocorticoids and apoptosis. However, the ordering between lymphopenia and apoptosis appears different between SARS and COVID‐19 patients, ie, lymphopenia is prior to apoptosis in SARS patients whereas apoptosis is prior to lymphopenia in COVID‐19 patients. This paper attempts to figure out this contradiction through three players, lymphopenia, glucocorticoids, and apoptosis. Although the literature does not provide a solid explanation, the level of glucocorticoids could determine the ordering between lymphopenia and apoptosis because the administration of high doses of glucocorticoids could lead to lymphopenia whereas low doses of glucocorticoids could benefit patients. In the meantime, this paper raises several questions, which need to be answered in order to better understand the whole course of COVID‐19.

Role of the adaptive immune response in sepsis

Sepsis is a syndrome of shock and dysfunction of multiple vital organs that is caused by an uncontrolled immune response to infection and has a high mortality rate. There are no therapies for sepsis, and it has become a global cause for concern. Advances in patient care and management now mean that most patients survive the initial hyper-inflammatory phase of sepsis but progress to a later immunosuppressed phase, where 30% of patients die due to secondary infection. Deficits in the adaptive immune response may play a major role in sepsis patient mortality. The adaptive immune response involves a number of cell types including T cells, B cells and dendritic cells, all with immunoregulatory roles aimed at limiting damage and returning immune homeostasis after infection or insult. However, in sepsis, adaptive immune cells experience cell death or exhaustion, meaning that they have defective effector and memory responses ultimately resulting in an ineffective or suppressed immune defence. CD4+ T cells seem to be the most susceptible to cell death during sepsis and have ensuing defective secretory profiles and functions. Regulatory T cells seem to evade apoptosis and contribute to the immune suppression observed with sepsis. Preclinical studies have identified a number of new targets for therapy in sepsis including anti-apoptotic agents and monoclonal antibodies aimed at reducing cell death, exhaustion and maintaining/restoring adaptive immune cell functions. While early phase clinical trials have demonstrated safety and encouraging signals for biologic effect, larger scale clinical trial testing is required to determine whether these strategies will prove effective in improving outcomes from sepsis.

Circulating BiP/Grp78 is a novel prognostic marker for sepsis-mediated immune cell death

Sepsis remains to be a major contributor to mortality in ICUs, and immune suppression caused by immune cell apoptosis determines the overall patient survival. However, diagnosis of sepsis-induced lymphopenia remains problematic with no accurate prognostic techniques or biomarkers for cell death available. Developing reliable prognostic tools for sepsis-mediated cell death is not only important for identifying patients at increased risk of immune suppression but also to monitor treatment progress of currently trialed immunotherapy strategies. We have previously shown an important role for endoplasmic reticulum stress (ER stress) in inducing sepsis-mediated cell death and here report on the identification of a secreted form of the ER chaperone BiP (immunoglobulin binding protein) as a novel circulating prognostic biomarker for immune cell death and ER stress during sepsis. Using biochemical purification and mass spectrometry coupled with an established in vitro sepsis cell death assay, we identified BiP/Grp78 as a factor secreted by lipopolysaccharide-activated macrophages that is capable of inducing cell death in target cells. Quantitative ELISA analysis showed significantly elevated levels of circulating BiP in mice undergoing polymicrobial sepsis, which was absent in Bim^-/- mice that are protected from sepsis-induced lymphopenia. Using blood serum from human sepsis patients, we could detect a significant difference in levels of secreted BiP in sepsis patients compared to nonseptic controls, suggesting that secreted circulating BiP could indeed be used as a prognostic marker that is directly correlative to immune cell death during sepsis.

The Critical Roles and Mechanisms of Immune Cell Death in Sepsis

Sepsis was first described by the ancient Greek physicians over 2000 years ago. The pathophysiology of the disease, however, is still not fully understood and hence the mortality rate is still unacceptably high due to lack of specific therapies. In the last decade, great progress has been made by shifting the focus of research from systemic inflammatory response syndrome (SIRS) to multiple organ dysfunction syndrome (MODS). Sepsis has been re-defined as infection-induced MODS in 2016. How infection leads to MODS is not clear, but what mediates MODS becomes the major topic in understanding the molecular mechanisms and developing specific therapies. Recently, the mechanism of infection-induced extensive immune cell death which releases a large quantity of damage-associated molecular patterns (DAMPs) and their roles in the development of MODS as well as immunosuppression during sepsis have attracted much attention. Growing evidence supports the hypothesis that DAMPs, including high-mobility group box 1 protein (HMGB1), cell-free DNA (cfDNA) and histones as well as neutrophil extracellular traps (NETs), may directly or indirectly contribute significantly to the development of MODS. Here, we provide an overview of the mechanisms and consequences of infection-induced extensive immune cell death during the development of sepsis. We also propose a pivotal pathway from a local infection to eventual sepsis and a potential combined therapeutic strategy for targeting sepsis.

Circulating Bcl-2 concentrations and septic patient mortality

INTRODUCTION

There are not data on blood B-cell lymphoma 2 (Bcl-2) concentrations (one of the antiapoptotic molecules of the Bcl-2 family in the intrinsic apoptosis pathway) in septic patients. Therefore, this study was carried with the aims to explore whether blood Bcl-2 concentrations at diagnosis of sepsis are different in survivor and non-survivor septic patients, are associated with mortality, and are useful for the mortality prediction.

METHODS

Intensive Care Units from 3 Spanish hospitals participated in this observational and prospective study with septic patients and serum Bcl-2 concentrations at diagnosis of sepsis were determined. Mortality at 30 days was as outcome variable.

RESULTS

We found that 30-day non-surviving patients (n=81) showed lower serum Bcl-2 levels (p=0.003) than surviving patients (n=140). We found that serum concentrations of Bcl-2<4.4ng/mL were associated with mortality (OR=3.228; 95% CI=1.406-7.415; p=0.006) in the multiple logistic regression analysis, and that showed an area under the curve for mortality prediction of 62% (95% CI=55-68%; p=0.003).

CONCLUSIONS

In our study appears novel findings such as higher blood Bcl-2 concentrations in survivor than in non-survivor septic patients, the association between low blood Bcl-2 concentrations and mortality of septic patients, and the ability of blood Bcl-2 concentrations for the prediction of septic patient mortality.

B lymphocytopenia and Bregs in a not-to-die murine sepsis model

Sepsis is a leading cause of mortality in intensive care units due to multi-organ failure caused by dysregulated immune reactions. In this study, kinetic changes in the immune system were analyzed for 72 h in cecal ligation and puncture (CLP)-induced septic mice while preventing animal death by keeping body temperature. Increase of myeloid cells and decrease of B cells in circulation at 6 h after CLP were markedly observed. At the same time point, interleukin (IL)-10 expressing CD5⁺ regulatory B cells (Bregs) appeared. IL-10 and programmed death-ligand 1 (PD-L1) mRNA as well as IL-1β, IL-6 and interferon γ (IFNγ) mRNA was increased in the spleen at 6 h. A gradual decrease in Bcl-2 and abrupt increase of Bim expression in the spleen at the late phase were also found. These results showed that B lymphocytopenia with the appearance of Bregs is the earliest event, likely leading to immunoparalysis in sepsis.

Evaluation of BCL2 and TNFα as mRNA biomarkers for monitoring the immune response in critically ill children

Background

Hospital acquired infection (HAI) and multiple organ dysfunctions (MODS) remain a leading cause of death in pediatric intensive care unit (PICU) despite the great efforts to control it.

Objective

Our objective was to assess the mRNA of TNFα and BCL2 for prediction of HAI and/or MODS in our community.

Patients and methods

Fifty children, admitted to PICU, were included in the study after exclusion of cases of end-stage renal failure, end-stage liver failure and congenital immune deficiency. Serial Blood samples were collected for complete blood count (CBC) and other routine investigations. Gene expression of (TNFα and BCL2) was quantified using quantitative real time PCR (qRT-PCR). Centers of disease control (CDC) criteria were used to detect HAI, and organ failure index (OFI). Pediatric logistic organ dysfunction (PELOD) and pediatric risk of mortality (PRISM) scores were used for follow up. The results were compared between the group who acquired HAI and who didn't. Gene expression was tested with a ROC curve to detect its ability to predict HAI.

Main results

The overall complication (HAI and/or MODS) rate was 52%, Complicated cases had a significantly longer duration of stay in PICU (0.002) and in overall hospital stay (p = 0.013) and a higher death rate (p = 0.000). On day1; TNFα, BCL2 and lymphocytic count were lower in patients who developed complications (p = 0.02, p = 0.000 and p = 0.04, respectively), all had the ability to predict the complications with AUC (0.7, 0.8 and 0.67 respectively). On day 4: TNFα and BCL2 returned to normal levels while the lymphocytic count still lower in complicated cases, p = 0.001 and AUC = 0.73.

Conclusions

TNFα and BCL2 on admission can predict HAI and MODS (AUC = 0.7 and AUC = 0.8), but were of no use in the follow-up, however, the lymphocytic count is a rapid, easy and cheap test to assess the immune state with a good predictive and follow up values.

•

To our knowledge, our work is the 1^st to show mRNA biomarkers in acquired immunosuppressed critically ill Egyptian children.

•

The current study provides a new evidence that immune suppression can be measured and opens the way for further studies.

•

We mainly found that TNFα and BCL2 can predict HAI and MODS on admission but they were of no use in the follow-up.

•

Lymphocytic count, a rapid, easy and cheap test, can assess the immune state with a good predictive and follow up values.

Endogenous H2S resists mitochondria-mediated apoptosis in the adrenal glands via ATP5A1 S-sulfhydration in male mice

In a previous study, we showed that endogenous hydrogen sulfide (H₂S) plays a key role in the maintenance of intact adrenal cortex function via the protection of mitochondrial function during endoxemia. We further investigated whether mitochondria-mediated apoptosis is involved in H₂S protection of adrenal function. LPS treatment resulted in mitochondria-mediated apoptosis in the adrenal glands of male mice, and these effects were prevented by the H₂S donor GYY4137. In the model of Y1 cells, the LPS-induced mitochondria-mediated apoptosis and blunt response to ACTH were rescued by GYY4137. The H₂S-generating enzyme cystathionine-β-synthase (CBS) knockout heterozygous (CBS^+/-) mice showed mitochondria-mediated apoptosis in the adrenal gland and adrenal insufficiency. GYY4137 treatment restored adrenal function and eliminated mitochondria-mediated apoptosis. Maleimide assay combined with mass spectrometry analysis showed that a number of proteins in mitochondria were S-sulfhydrated in the adrenal gland. ATP5A1 was further confirmed as S-sulfhydrated using a modified biotin switch assay. The level of S-sulfhydrated ATP5A1 was decreased in the adrenal gland of endotoxemic and CBS^+/- mice, which was restored by GYY4137. ATP5A1 was identified as sulfhydrated at cysteine 244 by H₂S. Overexpression of the cysteine 244 mutant ATP5A1 in Y1 cells resulted in a loss of LPS-induced mitochondria-mediated apoptosis and GYY4137 restoration of LPS-induced hyporesponsiveness to ACTH. Collectively, the present study revealed that decreased H₂S generation leads to mitochondrial-mediated apoptosis in the adrenal cortex and a blunt response to ACTH. S-sulfhydration of ATP5A1 at cysteine 244 is an important molecular mechanism by which H₂S maintains mitochondrial function and steroidogenesis in the adrenal glands.

Apoptosis-induced lymphopenia in sepsis and other severe injuries

Sepsis and other acute injuries such as severe trauma, extensive burns, or major surgeries, are usually followed by a period of marked immunosuppression. In particular, while lymphocytes play a pivotal role in immune response, their functions and numbers are profoundly altered after severe injuries. Apoptosis plays a central role in this process by affecting immune response at various levels. Indeed, apoptosis-induced lymphopenia duration and depth have been associated with higher risk of infection and mortality in various clinical settings. Therapies modulating apoptosis represent an interesting approach to restore immune competence after acute injury, although their use in clinical practice still presents several limitations. After briefly describing the apoptosis process in physiology and during severe injuries, we will explore the immunological consequences of injury-induced lymphocyte apoptosis, and describe associations with clinically relevant outcomes in patients. Therapeutic perspectives targeting apoptosis will also be discussed.

Clinical and Experimental Sepsis Impairs CD8 T-Cell-Mediated Immunity

Septic patients experience chronic immunosuppression resulting in enhanced susceptibility to infections normally controlled by T cells. Clinical research on septic patients has shown increased apoptosis and reduced total numbers of CD4 and CD8 T cells, suggesting contributing mechanism driving immunosuppression. Experimental models of sepsis, including cecal ligation and puncture, reverse translated this clinical observation to facilitate hypothesis-driven research and allow the use of an array of experimental tools to probe the impact of sepsis on T-cell immunity. In addition to numerical loss, sepsis functionally impairs the antigen-driven proliferative capacity and effector functions of CD4 and CD8 T cells. Sepsis-induced impairments in both the quantity and quality of T cells results in reduced protective capacity and increased susceptibility of mice to new or previously encountered infections. Therefore, the combined efforts of clinical and experimental sepsis research have begun to elucidate the impact of sepsis on T-cell-mediated immunity and potential T-cell-intrinsic and -extrinsic mechanisms driving chronic immunosuppression. Future work will explore the impact of sepsis on the recently appreciated tissue-resident memory (TRM) T cells, which provide robust protection against localized infections, and dendritic cells, which are needed to activate T cells and promote effective T-cell responses.

Skeletal Muscle and Lymphocyte Mitochondrial Dysfunctions in Septic Shock Trigger ICU-Acquired Weakness and Sepsis-Induced Immunoparalysis

Fundamental events driving the pathological processes of septic shock-induced multiorgan failure (MOF) at the cellular and subcellular levels remain debated. Emerging data implicate mitochondrial dysfunction as a critical factor in the pathogenesis of sepsis-associated MOF. If macrocirculatory and microcirculatory dysfunctions undoubtedly participate in organ dysfunction at the early stage of septic shock, an intrinsic bioenergetic failure, sometimes called "cytopathic hypoxia," perpetuates cellular dysfunction. Short-term failure of vital organs immediately threatens patient survival but long-term recovery is also severely hindered by persistent dysfunction of organs traditionally described as nonvital, such as skeletal muscle and peripheral blood mononuclear cells (PBMCs). In this review, we will stress how and why a persistent mitochondrial dysfunction in skeletal muscles and PBMC could impair survival in patients who overcome the first acute phase of their septic episode. First, muscle wasting protracts weaning from mechanical ventilation, increases the risk of mechanical ventilator-associated pneumonia, and creates a state of ICU-acquired muscle weakness, compelling the patient to bed. Second, failure of the immune system ("immunoparalysis") translates into its inability to clear infectious foci and predisposes the patient to recurrent nosocomial infections. We will finally emphasize how mitochondrial-targeted therapies could represent a realistic strategy to promote long-term recovery after sepsis.

Chemical chaperone TUDCA prevents apoptosis and improves survival during polymicrobial sepsis in mice

Sepsis-induced lymphopenia is a major cause of morbidities in intensive care units and in populations with chronic conditions such as renal failure, diabetes, HIV and alcohol abuse. Currently, other than supportive care and antibiotics, there are no treatments for this condition. We developed an in vitro assay to understand the role of the ER-stress-mediated apoptosis process in lymphocyte death during polymicrobial sepsis, which was reproducible in in vivo mouse models. Modulating ER stress using chemical chaperones significantly reduced the induction of the pro-apoptotic protein Bim both in vitro and in mice. Furthermore, in a ‘two-hit’ pneumonia model in mice, we have been able to demonstrate that administration of the chemical chaperone TUDCA helped to maintain lymphocyte homeostasis by significantly reducing lymphocyte apoptosis and this correlated with four-fold improvement in survival. Our results demonstrate a novel therapeutic opportunity for treating sepsis-induced lymphopenia in humans.

BH3-Only Proteins in Health and Disease

BH3-only proteins are proapoptotic members of the broader Bcl-2 family, which promote cell death by directly or indirectly activating Bax and Bak. The expression of BH3-only proteins is regulated both transcriptionally and posttranscriptionally in a cell type-specific and a tissue-specific manner. Research over the last 20 years has provided significant insights into their roles in tissue homeostasis and various pathologies, which in turn has led to the development of novel therapeutics for numerous diseases. In this review, a snapshot of the progress over this period is given, including our current understanding of their regulation, mode of action, role in mammalian development, and pathology.

Immunotherapy: A promising approach to reverse sepsis-induced immunosuppression

Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host responses to infection (Third International Consensus definition for Sepsis and septic shock). Despite decades of research, sepsis remains the leading cause of death in intensive care units. More than 40 clinical trials, most of which have targeted the sepsis-associated pro-inflammatory response, have failed. Thus, antibiotics and fluid resuscitation remain the mainstays of supportive care and there is intense need to discover and develop novel, targeted therapies to treat sepsis. Both pre-clinical and clinical studies over the past decade demonstrate unequivocally that sepsis not only causes hyper-inflammation, but also leads to simultaneous adaptive immune system dysfunction and impaired antimicrobial immunity. Evidences for immunosuppression include immune cell depletion (T cells most affected), compromised T cell effector functions, T cell exhaustion, impaired antigen presentation, increased susceptibility to opportunistic nosocomial infections, dysregulated cytokine secretion, and reactivation of latent viruses. Therefore, targeting immunosuppression provides a logical approach to treat protracted sepsis. Numerous pre-clinical studies using immunomodulatory agents such as interleukin-7, anti-programmed cell death 1 antibody (anti-PD-1), anti-programmed cell death 1 ligand antibody (anti-PD-L1), and others have demonstrated reversal of T cell dysfunction and improved survival. Therefore, identifying immunosuppressed patients with the help of specific biomarkers and administering specific immunomodulators holds significant potential for sepsis therapy in the future. This review focusses on T cell dysfunction during sepsis and discusses the potential immunotherapeutic agents to boost T cell function during sepsis and improve host resistance to infection.

Evaluation of mRNA Biomarkers to Identify Risk of Hospital Acquired Infections in Children Admitted to Paediatric Intensive Care Unit

Objectives

Hospital-acquired infections (HAI) are associated with significant mortality and morbidity and prolongation of hospital stay, adding strain on limited hospital resources. Despite stringent infection control practices some children remain at high risk of developing HAI. The development of biomarkers which could identify these patients would be useful. In this study our objective was to evaluate mRNA candidate biomarkers for HAI prediction in a pediatric intensive care unit.

Design

Serial blood samples were collected from patients admitted to pediatric intensive care unit between March and June 2012. Candidate gene expression (IL1B, TNF, IL10, CD3D, BCL2, BID) was quantified using RT-qPCR. Comparisons of relative gene expression between those that did not develop HAI versus those that did were performed using Mann Whitney U-test.

Patients

Exclusion criteria were: age <28 days or ≥16 years, expected length of stay < 24 hours, expected survival < 28 days, end-stage renal disease and end-stage liver disease. Finally, 45 children were included in this study.

Main Results

The overall HAI rate was 30% of which 62% were respiratory infections. Children who developed HAI had a three-fold increase in hospital stay compared to those who did not (27 days versus 9 days, p<0.001). An increased expression of cytokine genes (IL1B and IL10) was observed in patients who developed HAI, as well as a pro-apoptosis pattern (higher expression of BID and lower expression of BCL2). CD3D, a key TCR co-factor was also significantly down-modulated in patients who developed HAI.

Conclusions

To our knowledge, this is the first study of mRNA biomarkers of HAI in the paediatric population. Increased mRNA expressions of anti-inflammatory cytokine and modulation of apoptotic genes suggest the development of immunosuppression in critically ill children. Immune monitoring using a panel of genes may offer a novel stratification tool to identify HAI risk.

Full activation of CD4+ T cells early during sepsis requires specific antigen

Supplemental digital content is available in the text.

During sepsis, CD4⁺ T cells express activation markers within the first 24 h. In the present study, the mechanisms of T-cell activation and its consequences were addressed in an acute peritonitis model in mice. The response of CD4⁺ T cells to sepsis induction was compared between OTII mice, characterized by ovalbumin-specific T-cell receptor–transgenic T cells, and C57BL/6 controls (wild type [WT] mice). Because ovalbumin was absent during peritonitis, the OTII CD4⁺ T cells could not be activated by canonical antigen recognition. In both OTII and WT control mice, CD4⁺ T effector cells and CD4⁺ Foxp3⁺ regulatory T cells (Tregs) expressed the activation marker CD69 early after sepsis onset. However, full activation with upregulation of CD25 and proliferation took place only in the presence of the antigen. Besides this, the fraction of Tregs was lower in OTII than that in WT mice. Sepsis mortality was increased in OTII mice. Our data show that, in sepsis, partial activation of CD4⁺ T cells is induced by a T-cell receptor–independent pathway, whereas full stimulation and proliferation require a specific antigen. Antigen-dependent T-cell effector functions as well as Treg activity may contribute to sepsis survival.

Effect of Regulatory T Cells on Promoting Apoptosis of T Lymphocyte and Its Regulatory Mechanism in Sepsis

With both in vivo and in vitro experiments, the present study was conducted to investigate the effect of regulatory T cell (Treg) on promoting T-lymphocyte apoptosis and its regulatory mechanism through transforming growth factor-beta (TGF-β1) signaling in mice. A murine model of polymicrobial sepsis was reproduced by cecal ligation and puncture (CLP); PC61 and anti-TGF-β antibodies were used to decrease counts of CD4(+)CD25(+) Tregs and inhibit TGF-β activity, respectively. Splenic CD4(+)CD25(+) Tregs and CD4(+)CD25(-) T cells were isolated. Phenotypes, including cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), forkhead/winged helix transcription factor p3 (Foxp3), and TGFβ1(m+), as well as the apoptotic rate of CD4(+)CD25(-) T cell, were analyzed by flow cytometry. Real-time reverse transcription-polymerase chain reaction was performed to determine mRNA expression of TGF-β1, and the expressions of Smad2/Smad3, Bcl-2 superfamily members of Bcl-2/Bim, cytochrome C, the mitochondrial membrane potential, and caspases in CD4(+)CD25(-) T cells were simultaneously determined. After treatment with PC61 or anti-TGF-β antibody, CTLA-4, Foxp3, and TGFβ1(m+) expressions of CD4(+)CD25(+) Tregs were markedly decreased in comparison to that of the CLP group and the apoptosis rate of CD4(+)CD25(-) T cells was significantly positively correlated with the expression of TGF-β1. Meanwhile, levels of P-Smad2/P-Smad3, proapoptotic protein Bim, cytochrome C, and activity of caspase-3, -8, -9 were downregulated, whereas the mitochondrial membrane potential and antiapoptotic protein Bcl-2 expression were restored. Taken together, our data indicated that the TGF-β1 signal could be partly involved in the apoptosis of CD4(+)CD25(-) T cells promoted by CD4(+)CD25(+) Tregs, therefore inhibition of TGF-β1 expression may provide a novel strategy for the improvement of host immunosuppression following sepsis.

Dynamic expression of leukocyte innate immune genes in whole blood from horses with lipopolysaccharide-induced acute systemic inflammation

Background

In horses, insights into the innate immune processes in acute systemic inflammation are limited even though these processes may be highly important for future diagnostic and therapeutic advances in high-mortality disease conditions as the systemic inflammatory response syndrome (SIRS) and sepsis. Therefore, the aim of this study was to investigate the expression of 31 selected blood leukocyte immune genes in an equine model of acute systemic inflammation to identify significantly regulated genes and to describe their expression dynamics during a 24-h experimental period. Systemic inflammation was induced in 6 adult horses by the intravenous injection of 1 μg lipopolysaccharide (LPS) per kg btw. Sixteen blood samples were collected for each horse at predetermined intervals and analyzed by reverse transcription quantitative real-time PCR. Post-induction expression levels for each gene were compared with baseline levels.

Results

Systemic inflammation was confirmed by the presence of clinical and hematological changes which were consistent with SIRS. The clinical response to LPS was transient and brief as all horses except one showed unaltered general demeanor after 24 h. Twenty-two leukocyte genes were significantly regulated at at least one time point during the experimental period. By close inspection of the temporal responses the dynamic changes in mRNA abundance revealed a very rapid onset of both pro- and anti-inflammatory mediators and a substantial variation in both expression magnitudes and duration of changes between genes. A majority of the 22 significantly regulated genes peaked within the first 8 h after induction, and an on-going, albeit tightly controlled, regulation was seen after 24 h despite approximate clinical recovery.

Conclusions

This first broad study of gene expressions in blood leukocytes during equine acute LPS-induced systemic inflammation thoroughly characterized a highly regulated and dynamic innate immune response. These results provide new insights into the molecular mechanisms of equine systemic inflammation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-015-0450-5) contains supplementary material, which is available to authorized users.

Impact of Conditional miRNA126 Overexpression on Apoptosis-Resistant Endothelial Cell Production

The activation of endothelial cells is essential to repair damage caused by atherosclerosis via endothelial cell proliferation and migration. Overexpression of VEGF (vascular endothelial growth factor) and the downstream gene, B-cell lymphoma-2 (BCL-2) could result in apoptosis-resistant endothelial cells, which are responsible for aggravated hyperplasia and instable plaques generation. Previous studies have shown that miRNA126 could regulate the expression of VEGF. Here, we verified the existence of a miRNA126 binding site in VEGF’s 3’UTR. Additionally, VEGF regulated BCL-2 expression via AP1 (Activator Protein 1) binding site in BCL-2’s promoter. Next, we established an apoptosis-resistant endothelial cell line and constructed a lentiviral vector to express miRNA126 under the control of the BCL-2 promoter to investigate whether conditional expression of miRNA126 could modulate VEGF and BCL-2 expression in apoptosis-resistant endothelial cells. This lentiviral system specifically expressed miRNA126 in cells with high BCL-2 levels, downregulated VEGF expression, inhibited MAPK pathway activation and downregulated BCL-2 expression via suppression of AP1, and as a whole, reduced apoptosis-resistant endothelial cells, while the effects of miRNA126 on normal endothelial cells were relatively small. Our results demonstrate that conditional miRNA126 overexpression under the control of the downstream BCL-2 promoter provides a flexible regulatory strategy for reducing the apoptosis-resistant endothelial cells without having a significant impact on normal endothelial cells.

BH3-only proteins: a 20-year stock-take

BH3-only proteins are the sentinels of cellular stress, and their activation commits cells to apoptosis. Since the discovery of the first BH3-only protein BAD almost 20 years ago, at least seven more BH3-only proteins have been identified in mammals. They are regulated by a variety of environmental stimuli or by developmental cues, and play a crucial role in cellular homeostasis. Some are considered to be tumor suppressors, and also play a significant role in other pathologies. Their non-apoptotic functions are controversial, but there is broad consensus emerging regarding their role in apoptosis, which may help in designing better therapeutic agents for treating a variety of human diseases.

Insights into the apoptotic death of immune cells in sepsis

Sepsis with subsequent multiple-organ dysfunction is a distinct systemic inflammatory response to concealed or obvious infection, and it is a leading cause of death in intensive care units. Thus, one of the key goals in critical care medicine is to develop novel therapeutic strategies that will affect favorably on outcome of septic patients. In addition to systemic response to infection, apoptosis is implicated to be an important mechanism of the death of immune cells, including neutrophils, macrophages, T lymphocytes, and dendritic cells, and it is usually followed by the development of multiple-organ failure in sepsis. The implication of apoptosis of immune cells is now highlighted by multiple studies that demonstrate that prevention of cell apoptosis can improve survival in relevant animal models of severe sepsis. In this review, we focus on major apoptotic death pathways and molecular mechanisms that regulate apoptosis of different immune cells, and advances in these areas that may be translated into more promising therapies for the prevention and treatment of severe sepsis.

Pathophysiological aspects of sepsis: an overview

Sepsis is defined as severe systemic inflammation in response to invading pathogens, or an uncontrolled hyperinflammatory response, as mediated by the release of various proinflammatory mediators. Although some patients may die rapidly from septic shock accompanied by an overwhelming systemic inflammatory response syndrome (SIRS) triggered by a highly virulent pathogen, most patients survive the initial phase of sepsis, showing multiple organ damage days or weeks later. These patients often demonstrate signs of immune suppression accompanied by enhanced inflammation. Sepsis is a result of a complex process; there is interaction of various pathways, such as inflammation, immunity, coagulation, as well as the neuroendocrine system. This treatise is an attempt to provide a summary of several key regulatory mechanisms and to present the currently recognized molecular pathways that are involved in the pathogenesis of sepsis.

BH3-only proteins contribute to steatotic liver ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) to the liver continues to be a source of significant morbidity, especially in patients with hepatic steatosis. This is a growing problem given the increase in nonalcoholic fatty liver disease. B-cell lymphoma-2 homology3-only members of the B-cell lymphoma-2 protein family are known mediators of cellular apoptosis, although their role in hepatic IRI is still emerging. The goal of this study was to investigate the effect of Bim and Bid on warm hepatic IRI in the setting of steatosis.

METHODS

Lean and obese Bim and/or Bid wild-type (WT) and double knockout (DKO) mice underwent 60 min of warm hepatic ischemia using a 70% segmental occlusion technique. Obesity and hepatic steatosis were induced using a high fat diet. Hepatocellular injury patterns were compared among lean and steatotic mice after reperfusion. Differences were analyzed using a Student t-test and reported as mean ± standard error of the mean.

RESULTS

DKO mice were protected from IRI relative to WT. A high fat diet created equal degrees of steatosis in both WT and DKO mice. The IRI was increased in steatotic WT livers; however, DKO mice remained protected relative to WT despite hepatic steatosis.

CONCLUSIONS

The B-cell lymphoma-2 homology3-only proteins are important mediators of hepatic IRI in both lean and steatotic livers. These mechanisms have been underappreciated in steatotic liver injury and may be leveraged as targets for intervention in clinical scenarios such as transplant and hypovolemic shock.

Impact of sepsis on CD4 T cell immunity

Sepsis remains the primary cause of death from infection in hospital patients, despite improvements in antibiotics and intensive-care practices. Patients who survive severe sepsis can display suppressed immune function, often manifested as an increased susceptibility to (and mortality from) nosocomial infections. Not only is there a significant reduction in the number of various immune cell populations during sepsis, but there is also decreased function in the remaining lymphocytes. Within the immune system, CD4 T cells are important players in the proper development of numerous cellular and humoral immune responses. Despite sufficient clinical evidence of CD4 T cell loss in septic patients of all ages, the impact of sepsis on CD4 T cell responses is not well understood. Recent findings suggest that CD4 T cell impairment is a multipronged problem that results from initial sepsis-induced cell loss. However, the subsequent lymphopenia-induced numerical recovery of the CD4 T cell compartment leads to intrinsic alterations in phenotype and effector function, reduced repertoire diversity, changes in the composition of naive antigen-specific CD4 T cell pools, and changes in the representation of different CD4 T cell subpopulations (e.g., increases in Treg frequency). This review focuses on sepsis-induced alterations within the CD4 T cell compartment that influence the ability of the immune system to control secondary heterologous infections. The understanding of how sepsis affects CD4 T cells through their numerical loss and recovery, as well as function, is important in the development of future treatments designed to restore CD4 T cells to their presepsis state.

Uncontrolled sepsis: a systematic review of translational immunology studies in intensive care medicine

BACKGROUND

The design of clinical immunology studies in sepsis presents several fundamental challenges to improving the translational understanding of pathologic mechanisms. We undertook a systematic review of bed-to-benchside studies to test the hypothesis that variable clinical design methodologies used to investigate immunologic function in sepsis contribute to apparently conflicting laboratory data, and identify potential alternatives that overcome various obstacles to improve experimental design.

METHODS

We performed a systematic review of the design methodology employed to study neutrophil function (respiratory burst), monocyte endotoxin tolerance and lymphocyte apoptosis in the intensive care setting, over the past 15 years. We specifically focussed on how control samples were defined, taking into account age, gender, ethnicity, concomitant therapies, timing of sample collection and the criteria used to diagnose sepsis.

RESULTS

We identified 57 eligible studies, the majority of which (74%) used case-control methodology. Healthy volunteers represented the control population selected in 83% of studies. Comprehensive demographic data on age, gender and ethnicity were provided in ≤48% of case control studies. Documentation of diseases associated with immunosuppression, malignancy and immunomodulatory therapies was rare. Less than half (44%) of studies undertook independent adjudication for the diagnosis of sepsis while 68% provided microbiological data. The timing of sample collection was defined by highly variable clinical criteria. By contrast, surgical studies avoided many such confounders, although only one study in surgical patients monitored the study group for development of sepsis.

CONCLUSIONS

We found several important and common limitations in the clinical design of translational immunologic studies in human sepsis. Major elective surgery overcame many of these methodological limitations. The failure of adequate clinical design in mechanistic studies may contribute to the lack of translational therapeutic progress in intensive care medicine.

Sepsis-induced immunosuppression: from cellular dysfunctions to immunotherapy

Sepsis - which is a severe life-threatening infection with organ dysfunction - initiates a complex interplay of host pro-inflammatory and anti-inflammatory processes. Sepsis can be considered a race to the death between the pathogens and the host immune system, and it is the proper balance between the often competing pro- and anti-inflammatory pathways that determines the fate of the individual. Although the field of sepsis research has witnessed the failure of many highly touted clinical trials, a better understanding of the pathophysiological basis of the disorder and the mechanisms responsible for the associated pro- and anti-inflammatory responses provides a novel approach for treating this highly lethal condition. Biomarker-guided immunotherapy that is administered to patients at the proper immune phase of sepsis is potentially a major advance in the treatment of sepsis and in the field of infectious disease.

The significance and regulatory mechanisms of innate immune cells in the development of sepsis

Sepsis with subsequent multiple organ dysfunction is a pronounced systemic inflammatory response to concealed or known infection and is a leading cause of death in intensive care units. The survival rate of severe sepsis and septic shock has not markedly improved in recent decades despite a great number of receptors and molecules involved in its pathogenesis have been found and taken as therapeutic targets. It is essential to thoroughly understand the host cell-mediated immunity involved in the development of sepsis and sepsis-related organ injury. Recent studies indicate that innate immune cells (such as neutrophils, macrophages, dendritic cells, T lymphocytes, regulatory T cells, and natural killer T cells) play pivotal roles in the maintenance of peripheral homeostasis and regulation of immune responses during sepsis. Therefore, an understanding of the biological significance and pathophysiological roles of different cell populations might gain novel insights into the immunoregulatory mechanisms of sepsis. In this review, we focus on major immune cells that may play potential roles in the contribution of new therapeutic approaches for sepsis.

Glucose starvation induces cell death in K-ras-transformed cells by interfering with the hexosamine biosynthesis pathway and activating the unfolded protein response

Cancer cells, which use more glucose than normal cells and accumulate extracellular lactate even under normoxic conditions (Warburg effect), have been reported to undergo cell death under glucose deprivation, whereas normal cells remain viable. As it may be relevant to exploit the molecular mechanisms underlying this biological response to achieve new cancer therapies, in this paper we sought to identify them by using transcriptome and proteome analysis applied to an established glucose-addicted cellular model of transformation, namely, murine NIH-3T3 fibroblasts harboring an oncogenic K-RAS gene, compared with parental cells. Noteworthy is that the analyses performed in high- and low-glucose cultures indicate that reduction of glucose availability induces, especially in transformed cells, a significant increase in the expression of several unfolded protein response (UPR) hallmark genes. We show that this response is strictly associated with transformed cell death, given that its attenuation, by reducing protein translation or by increasing cell protein folding capacity, preserves the survival of transformed cells. Such an effect is also observed by inhibiting c-Jun NH2-terminal kinase, a pro-apoptotic signaling mediator set downstream of UPR. Strikingly, addition of N-acetyl-𝒟-glucosamine, a specific substrate for the hexosamine biosynthesis pathway (HBP), to glucose-depleted cells completely prevents transformed cell death, stressing the important role of glucose in HBP fuelling to ensure UPR attenuation and increased cell survival. Interestingly, these results have been fully recognized in a human model of breast cancer, MDA-MB-231 cells. In conclusion, we show that glucose deprivation, leading to harmful accumulation of unfolded proteins in consequence of a reduction of protein glycosylation, induces a UPR-dependent cell death mechanism. These findings may open the way for new therapeutic strategies to specifically kill glycolytic cancer cells.

Different changes in mitochondrial apoptotic pathway in lymphocytes and granulocytes in cirrhotic patients with sepsis

BACKGROUND & AIMS

Apoptosis regulates leucocyte response during bacterial infections. This study explored leucocyte apoptotic pathway in cirrhotic patients with or without infections or sepsis.

METHODS

In cirrhotic patients with bacterial infection or sepsis, the expression of Caspase 9, Bcl-2 family proteins, which comprises pro-apoptotic molecules, such as Bax, and anti-apoptotic molecules, such as Bcl-2 and Bcl-xL, were measured in peripheral lymphocytes and granulocytes. Regulatory microRNAs MIR-15 and MIR-16 were also measured.

RESULTS

This study enrolled 80 patients with cirrhosis, of whom 28 had no evidence of infections, 32 had bacterial infections and 20 had sepsis; reference values were obtained from 10 age-matched healthy subjects. An over-expression of Caspase-9 and pro-apoptotic protein Bax was found in lymphocytes of cirrhotic patients with infection or sepsis as compared with non-infected cases (P = 0.05 and 0.0001, respectively), while anti-apoptotic proteins Bcl-2 and Bcl-xL were downregulated. In granulocytes, lowest expression of pro-apoptotic protein Bax occurred in septic patients, while in cirrhotics with infections anti-apoptotic Bcl-2 and Bcl-xL were upregulated. Eight patients died; the survivors had less derangements in Bax, Bcl-2 and BcL-xL expression than non-survivors. The pro-apoptotic miRNA, MIR-15 and MIR-16, were upregulated in cirrhotics with bacterial infections.

CONCLUSIONS

Overall, the data show in lymphocytes, and not in granulocytes, an activation of the pro-apoptotic pathway in cirrhotic patients with bacterial infections, which correlates with the severity of the infection and the outcome.

Is suppression of apoptosis a new therapeutic target in sepsis?

Sepsis remains as a leading cause of death in critically ill patients. Unfortunately, there have been very few successful specific therapeutic agents that can significantly reduce the attributable mortality and morbidity of sepsis. Developing novel therapeutic strategies to improve outcomes of sepsis remains an important focus of ongoing research in the field of critical care medicine. Apoptosis has recently been identified as an important mechanism of cell death and evidence suggests that prevention of cell apoptosis can improve survival in animal models of sepsis and endotoxaemia. In this review article, we summarise the critical role of apoptosis of the immune cells in the pathophysiology of sepsis and propose that blocking cell-signaling pathways leading to apoptosis may present a promising specific therapy for sepsis. Various methods to inhibit apoptosis including the cell surface Fas receptor pathway inhibitors, caspase inhibitors, over-expression of anti-apoptotic genes and small interfering ribonucleic acid therapy are discussed.

A prospective analysis of lymphocyte phenotype and function over the course of acute sepsis

Introduction

Severe sepsis is characterized by an initial hyper-inflammatory response that may progress to an immune-suppressed state associated with increased susceptibility to nosocomial infection. Analysis of samples obtained from patients who died of sepsis has identified expression of specific inhibitory receptors expressed on lymphocytes that are associated with cell exhaustion. The objective of this study was to prospectively determine the pattern of expression of these receptors and immune cell function in patients with acute sepsis.

Methods

Twenty-four patients with severe sepsis were enrolled within 24 hours of the onset of sepsis, as were 12 age-matched healthy controls. Peripheral blood was obtained at enrollment and again seven days later. Immune cell subsets and receptor expression were extensively characterized by quantitative flow cytometry. Lymphocyte function was assayed by stimulated cytokine secretion and proliferation assays. Results were also correlated to clinical outcome.

Results

At the onset of severe sepsis, patients had decreased circulating innate and adaptive immune cells and elevated lymphocyte expression of receptors associated with cell activation compared to controls. Samples analyzed seven days later demonstrated increased expression of the inhibitory receptors CTLA4, TIM-3 and LAG-3 on T lymphocytes accompanied by decreased expression of the IL-7 receptor. Functional assays revealed impaired secretion of interferon γ following stimulation in vitro, which was reversible by incubation overnight in fresh media. Impaired secretion of IFNγ correlated with death or development of secondary infection.

Conclusions

Lymphocytes from patients with acute sepsis upregulate expression of receptors associated with cell exhaustion, which may contribute to the immune suppressed state that occurs in protracted disease. Therapy that reverses T cell exhaustion may restore immune function in immunocompromised patients and improve survival in sepsis.

Ventilator-associated pneumonia: bacteremia and death after traumatic injury

BACKGROUND

The implications of bacteremia in critically ill patients are uncertain. Some reports suggest bacteremia is linked to higher mortality whereas others do not. These differences may, in part, be because of differences in patient cohorts. To address the potential independent relationship between bacteremia and outcome, we focused on critically ill trauma patients with ventilator-associated pneumonia (VAP), of whom a significant proportion had concomitant bacteremia. We tested the hypothesis that bacteremia was associated with death in trauma patients who developed VAP.

METHODS

In this retrospective cohort study, we measured the incidence of bacteremia associated with VAP and compared the case-fatality rates between patients with and without bacteremia. We adjusted for other mortality risk factors and possible confounders in two ways. First, using forward conditional logistic regression and second, we calculated propensity scores and then adjusted for this score in a regression model.

RESULTS

There were 554 with VAP. Patients with bacteremia had a 26% case-fatality rate (19 of 74 patients). Patients with VAP alone had a case-fatality rate of 12% (56 of 480 patients). The unadjusted relative risk (RR) for death associated with bacteremia was 2.2 (95% confidence interval = 1.4-3.5). After adjusting for age, acute physiology score, and severity of injury, patients with bacteremia had an increased risk of death compared with patients with VAP alone (adjusted odds ratio = 2.65, 95% confidence interval = 1.36-5.17). Our propensity score analysis resulted in a similar association between bacteremia and mortality.

CONCLUSIONS

VAP with bacteremia is associated with an increased mortality in comparison with VAP alone after severe traumatic injury.

Molecular mechanisms underlying delayed apoptosis in neutrophils from multiple trauma patients with and without sepsis

Delayed neutrophil apoptosis and overshooting neutrophil activity contribute to organ dysfunction and subsequent organ failure in sepsis. Here, we investigated apoptotic signaling pathways that are involved in the inhibition of spontaneous apoptosis in neutrophils isolated from major trauma patients with uneventful outcome as well as in those with sepsis development. DNA fragmentation in peripheral blood neutrophils showed an inverse correlation with the organ dysfunction at d 10 after trauma in all patients, supporting the important role of neutrophil apoptosis regulation for patient's outcome. The expression of the antiapoptotic Bcl-2 protein members A1 and Mcl-1 were found to be diminished in the septic patients at d 5 and d 10 after trauma. This decrease was also linked to an impaired intrinsic apoptosis resistance, which has been previously shown to occur in neutrophils during systemic inflammation. In patients with sepsis development, delayed neutrophil apoptosis was found to be associated with a disturbed extrinsic pathway, as demonstrated by reduced caspase-8 activity and Bid truncation. Notably, the expression of Dad1 protein, which is involved in protein N-glycosylation, was significantly increased in septic patients at d 10 after trauma. Taken together, our data demonstrate that neutrophil apoptosis is regulated by both the intrinsic and extrinsic pathway, depending on patient's outcome. These findings might provide a molecular basis for new strategies targeting cell death pathways in apoptosis-resistant neutrophils during systemic inflammation.

[Reversing ICU-acquired immunosuppression: an innovative biomarker-guided therapeutic strategy for decreasing sepsis mortality and nosocomial infection rate]

Septic syndromes (systemic inflammatory response associated with infection) remain a major although largely under-recognized health care problem and represent the first cause of mortality in intensive care units. Regarding immune response, it is now agreed that sepsis induces an anti-inflammatory process, acting as a negative feedback. This inhibitory mechanism becomes deleterious as nearly all immune functions are rapidly compromised. The magnitude and persistence over time of this immunosuppression is correlated with nosocomial infections and mortality. Decreased HLA-DR expression on monocytes/increased percentage of regulatory T cells are biomarkers identifying patients at risk who could benefit from immunotherapy. This review attempts to integrate these new facts into an up-to-date account of sepsis pathophysiology.

Prevention of lymphocyte apoptosis in septic mice with cancer increases mortality

Lymphocyte apoptosis is thought to have a major role in the pathophysiology of sepsis. However, there is a disconnect between animal models of sepsis and patients with the disease, because the former use subjects that were healthy prior to the onset of infection while most patients have underlying comorbidities. The purpose of this study was to determine whether lymphocyte apoptosis prevention is effective in preventing mortality in septic mice with preexisting cancer. Mice with lymphocyte Bcl-2 overexpression (Bcl-2-Ig) and wild type (WT) mice were injected with a transplantable pancreatic adenocarcinoma cell line. Three weeks later, after development of palpable tumors, all animals received an intratracheal injection of Pseudomonas aeruginosa. Despite having decreased sepsis-induced T and B lymphocyte apoptosis, Bcl-2-Ig mice had markedly increased mortality compared with WT mice following P. aeruginosa pneumonia (85 versus 44% 7-d mortality; p = 0.004). The worsened survival in Bcl-2-Ig mice was associated with increases in Th1 cytokines TNF-α and IFN-γ in bronchoalveolar lavage fluid and decreased production of the Th2 cytokine IL-10 in stimulated splenocytes. There were no differences in tumor size or pulmonary pathology between Bcl-2-Ig and WT mice. To verify that the mortality difference was not specific to Bcl-2 overexpression, similar experiments were performed in Bim(-/-) mice. Septic Bim(-/-) mice with cancer also had increased mortality compared with septic WT mice with cancer. These data demonstrate that, despite overwhelming evidence that prevention of lymphocyte apoptosis is beneficial in septic hosts without comorbidities, the same strategy worsens survival in mice with cancer that are given pneumonia.